This invention relates to image capture and storage techniques in association with optical mark reading processes.
Optical mark reading ("OMR") is a technique by which "marks" on paper documents are "read" or identified by means of optical equipment.
Marks are typically made to indicate a response, reaction, opinion, name or title, or to signify other information. Marks are often made in "grids" of responses corresponding to letters, digits, alphanumeric codes, test item responses, etc. In some cases, marks are made by equipment: when documents are first produced, i.e. printed by a forms printer, marks may be "filled in" to identify the document type and/or provide a unique number for the specific document. In some cases, a computer controlled printer may be used to fill in marks, such as to complete sections which would otherwise need to be completed by a person. Although they have many applications, OMR forms are most widely used for recording answers to multiple choice tests. Other applications include surveys, questionnaires, inventory control and the like.
Marks can be detected optically by the absence or presence of light: if sufficient light is reflected by the paper at a specific location, there is no mark. If sufficient light is absorbed that the intensity of the reflected light is significantly reduced, a mark is detected.
OMR processing works only on marks located in predetermined locations, or "response positions." Most OMR equipment is designed to read a specific "matrix" of such marks, typically with a fixed number of responses per inch in both the horizontal and vertical directions. Typical matrices include 6" by 6" (i.e. six responses per inch on a row of responses, and six lines or rows per inch), "6 by 8", "6 by 5", and "8 by 6".
Once the equipment has detected the presence of a mark at a specific location, conventional OMR applications store an appropriate character, code, or value so that subsequent processing properly reflects or recognizes the response intended by the person or machine and signified by the mark.
In a typical OMR device, the optical device(s) used to detect marks are contained in a "read head" which is in a fixed location. As the document is moved past the read head, successive rows of response positions are detected and processed.
Most OMR devices operate with discrete optical sensors for each response position on a row. Such devices are known as "fixed matrix" devices. Other OMR devices, however, based on a "line scan" camera, can be controlled to accept different spacing of the response positions within each row. By controlling the spacing between responses, these devices can process documents printed in one of several different matrices. They are, therefore, known as "variable matrix" devices.